Microwave optical double resonance and continuous wave dye laser excitation spectroscopy of NO 2: Rotational assignment of the K = 0−4 subbands of the 593 nm band

Abstract

A rotational assignment of approximately 80 lines with K a ′ = 0, 1, 2, 3, and 4 has been made of the 593 nm 2A 1 → 2B 2 band of NO 2 using cw dye laser excitation and microwave optical double-resonance spectroscopy. Rotational constants for the 2 B 2 state were obtained as A = 8.52 cm −1, B = 0.458 cm −1, and C = 0.388 cm −1. Spin splittings for the K a ′ = 0 excited state levels fit a simple symmetric top formula and give (ϵ bb + ϵ cc) 2 = −0.0483 cm −1 . Spin splittings for K a ′ = 1 ( N′ even) are irregular and are shown to change sign between N′ = 6 and 8. Assuming that the large inertial defect of 4.66 amu Å 2 arises solely from A, a structure for the 2 B 2 state is obtained which gives r (NO) = 1.35 A ̊ and an ONO angle of 105°. Alternatively, weighting the three rotational constants equally gives r = 1.29 A ̊ and θ = 118°.